I. Field of the Invention
The present invention relates generally to spinal surgery and, more particularly, to a device for spinal fusion comprising a spinal fusion implant of non-bone construction to be introduced into an intervertebral disc space.
II. Discussion of the Prior Art
Currently there are nearly 500,000 spine lumbar and cervical fusion procedures performed each year in the United States. One of the causes of back pain and disability results from the rupture or degeneration of one or more intervertebral discs in the spine. Surgical procedures are commonly performed to correct problems with displaced, damaged, or degenerated intervertebral discs due to trauma, disease, or aging. Generally, spinal fusion procedures involve removing some or the all of the diseased or damaged disc, and inserting one or more intervertebral implants into the resulting disc space.
Minimally invasive methods of performing spinal fusion have gained popularity in recent years due to the many benefits of the procedure which include diminished dissection of body tissue and lower blood loss during surgery resulting in reduced surgery time, lower post-operative pain and a quicker recovery for patients. Anterior lumbar interbody fusion (ALIF) procedures provide access to a desired target site without harming back muscles and nerves. The ALIF technique involves approaching the spine through the abdomen and exposing the front of the spine, as opposed to the side or the back. Approaching the spine this way generally allows for greater exposure and a more complete excision of the damaged disc. Introducing the intervertebral implant serves to restore the height between adjacent vertebrae (“disc height”), which reduces if not eliminates neural impingement commonly associated with a damaged or diseased disc. Distraction of the disc space with subsequent decompression of nerve roots can be accomplished by rotating a device between the adjacent vertebrae.
Current spinal fusion implants utilize grafts of either bone or artificial implants to fill the intervertebral disc space. Spinal fusion implants or grafts may be made of metal, plastic composites, ceramics, or bone. Natural bone grafts have also been developed including autologous and allograft bone grafts. Other bone grafts may include certain man-made substances including binder joining bone chips and composite bone structures.
While generally effective, the use of bone grafts presents several disadvantages. Autologous bone grafts are obtained from bone material surgically removed from the iliac crest of a patient. This method can be detrimental because it may not yield a sufficient quantity of graft material, requires additional surgery, and increases the risk of infection and blood loss. Moreover, the structural integrity at the donor site can be reduced and significant morbidity associated with harvesting the autologous bone graft may occur.
Allograft bone grafts are obtained from cadaveric specimens, machined, and sterilized for implantation. However, allografts can be disadvantageous because of the risk of disease transmission and immune reactions. Further, production of allograft bone implants may be difficult because of the inherent challenges in forecasting the receipt of cadavers and allograft may only provide temporary support as it is difficult to manufacture the allograft with consistent shape and strength given the differing characteristics of cadavers. Graft material usually has a smooth surface which does not provide a good friction fit between the adjacent vertebrae and slippage of the graft may occur which can cause neural and vascular injury as well as collapse of the disc space.
A need remains for fusion implants that preserve the intradiscal space and support the vertebral column until the adjacent vertebrae are fused and still encourage bone ingrowth to achieve a solid fusion. A need also remains for implants which maximize surface contact with outer portions of vertebral anatomy while providing maximum area for fusion.
The present invention is directed at overcoming, or at least improving upon, the disadvantages of the prior art.